M87.173 Osteonecrosis due to drugs, unspecified ankle

Billable ICD-10-CM code, FY2026. Acts as a Complication or Comorbidity (CC) as a secondary diagnosis.

Applies from M87 Osteonecrosis

Includes

• avascular necrosis of bone

Excludes1 (never code together)

• juvenile osteonecrosis (M91-M92)
• osteochondropathies (M90-M93)

Use additional code

• code to identify major osseous defect, if applicable (M89.7-)

Applies from M87.1 Osteonecrosis due to drugs

Use additional code

• code for adverse effect, if applicable, to identify drug (T36-T50 with fifth or sixth character 5)

Risk adjustment (HCC)

• CMS-HCC V22: HCC 39 — Bone/Joint/Muscle Infections/Necrosis
• RxHCC V08: HCC 80 — Aseptic Necrosis of Bone
• ESRD V24: HCC 39

MS-DRG index

Defines the logic of DRG(s) 553-554 in MDC 08.

Approximate ICD-9-CM (GEMs)

• 733.49 Aseptic necrosis of bone, other (approximate)

Medicare Code Edits (MCE v43.1 (April 2026))

• Unspecified code (laterality): Unspecified codes for which a more specific code identifying laterality (right, left, bilateral) exists within the same code family.

Code annotations containing back-references to M87.173

Back-references to M87

• Code First: M89.7 Major osseous defect ("aseptic necrosis of bone (M87.-)")
• Code First: M89.7 Major osseous defect ("osteonecrosis (M87.-)")

Nearby codes

• M87.165 Osteonecrosis due to drugs, left fibula
• M87.166 Osteonecrosis due to drugs, unspecified fibula
• M87.17 Osteonecrosis due to drugs, ankle, foot and toes
• M87.171 Osteonecrosis due to drugs, right ankle
• M87.172 Osteonecrosis due to drugs, left ankle
• M87.173 Osteonecrosis due to drugs, unspecified ankle (this code)
• M87.174 Osteonecrosis due to drugs, right foot
• M87.175 Osteonecrosis due to drugs, left foot
• M87.176 Osteonecrosis due to drugs, unspecified foot
• M87.177 Osteonecrosis due to drugs, right toe(s)
• M87.178 Osteonecrosis due to drugs, left toe(s)